Expand and combine like terms. $(5a^3-6a^2)(5a^3+6a^2)=$
Answer: We can expand this expression like any product of two binomials. However, this expression has a special form that makes it easier to expand. This is the "difference of squares" form (where $P$ and $Q$ can be any monomial): $(P+Q)(P-Q)=P^2-Q^2$ $\begin{aligned} &\phantom{=}(5a^3-6a^2)(5a^3+6a^2) \\\\ &=\left(5a^3\right)^2-\left(6a^2\right)^2 \\\\ &=25a^6-36a^4 \end{aligned}$